Juno-UVS and Chandra Observations of Jupiter's Polar Auroral Emissions

EPSC Abstracts Vol. 11, EPSC2017-388, 2017 European Planetary Science Congress 2017 EEuropeaPn PlanetarSy Science CCongress c Author(s) 2017

Juno-UVS and Chandra Observations of Jupiter’s Polar Auroral Emissions

G. R. Gladstone (1,2), J. A. Kammer (1), M. H. Versteeg (1), T. K. Greathouse (1), V. Hue (1), J.-C. Gérard (3), D. Grodent (3), B. Bonfond (3), C. Jackman (4), G. Branduardi-Raymont (5), R. P. Kraft (6), W. R. Dunn (5), S. J. Bolton (1), J. E. P. Connerney (7), S. M. Levin (8), B. H. Mauk (9), P. Valek (1,2), A. Adriani (10), W. S. Kurth (11), and G. S. Orton (8) (1) Southwest Research Institute, San Antonio, TX, USA, (2) Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX, USA, (3) Université de Liège, Liège, Belgium, (4) University of Southampton, Southampton, UK (5) Mullard Space Science Laboratory, University College London, Holmbury St. Mary, UK, (6) Smithsonian Astrophysical Observatory, Cambridge, MA, USA (7) NASA Goddard Space Flight Center, Greenbelt, MD, USA, (8) Jet Propulsion Laboratory, Pasadena, CA, USA, (9) The Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA, (10) INAF-Istituto di Astrofisica e Planetologia Spaziali, Roma, Italy, (11) University of Iowa, Iowa City, IA, USA ([email protected] / Fax: 210-522-4520) Abstract entrance is used to observe at up to ±30° perpendicular to the Juno spin plane. Tantalum The Juno spacecraft polar orbit provides an excellent surrounds the spectrograph assembly to shield the platform for observing Jupiter’s bright and transient Juno-UVS MCP detector and its electronics from polar auroral emissions [1]. These emissions occur as high-energy electrons. The purpose of Juno-UVS is flares at far-ultraviolet (FUV) wavelengths [2], which to remotely sense Jupiter’s auroral morphology and have been associated with X-ray bursts [3]. During brightness to provide context for in situ 2017, joint Juno-UVS and Chandra HRC-I measurements by Juno’s particle instruments. observations are being executed during four Juno perijoves to further investigate these polar auroras. Using Chandra’s HRC-I camera, we are monitoring auroral X-ray emissions from Jupiter when the cusp region is in a good location for simultaneous 1. Polar Emissions observations by Juno-UVS and Chandra. Half the Ultraviolet and X-ray observations of Jupiter’s observations are planned to focus the northern cusp auroras have provided valuable insights into the and half on the southern cusp. Our primary goal is to fundamental processes of charged particle study the morphology of the cusp region emissions, acceleration and the resulting currents in Jupiter's comparing simultaneous high-spatial resolution magnetosphere [4]. The cusp or active regions of Chandra HRC-I observations with very-high spatial Jupiter’s polar auroras are the site of highly-variable resolution Juno-UVS observations to test different X-ray, FUV, and thermal-IR auroral emissions. The physical theories of the source of the emissions. northern hot spot is typically found near a system III longitude of 170º and latitude of 65º (easily seen During 2017, joint Juno-UVS and Chandra HRC-I from Earth), and the corresponding southern region is observations are planned for PJ4, PJ5, PJ6, and PJ7, visible when conditions are favorable, as they are and the results of observations through PJ8 will be during the Juno mission when the sub-Earth latitude presented at EPSC. is as far south as it can be). 3. Initial Results 2. Juno-UVS and Chandra Support Initial results for PJ4 are shown in Figs. 1-3, where Juno-UVS is an imaging spectrograph with a transient southern polar FUV emissions decrease bandpass of 70<λ<205 nm [5]. This wavelength markedly in brightness during the same period as a range includes important far-ultraviolet (FUV) large decrease in auroral X-ray brightness. Maps of the X-ray emissions will be compared with the FUV emissions from the H2 bands and the H Lyman series which are produced in Jupiter’s auroras, and also the maps to investigate these polar auroras further. absorption signatures of aurorally-produced hydrocarbons. A flat scan mirror situated near the

Figure 3: Histograms of X-ray count rates from the northern and southern auroras as observed by Chandra HRC-I during PJ4, corrected for one-way Figure 1: False color map of the southern aurora light time. The left and right pairs of vertical dashed observed by Juno-UVS in during PJ4 on 2 February green lines show the times presented in Figs. 1 and 2, 2017 13:50-14:00. Red colors indicate high FUV respectively. Note the ~6x drop in X-ray brightness color ratios. Juno magnetic footprints according to between these two periods, consistent with the drop VIP4 and VIPAL are indicated by green and yellow in FUV brightness. lines, respectively, which are thicker for the 10- minute period when Juno-UVS data were taken. Acknowledgements This research was funded by the National Aeronautics and Space Administration through the Juno Project.

References [1] Grodent, D.: A brief review of ultraviolet auroral emissions on giant planets, Space Sci. Rev., Vol. 187, pp. 23-50, 2015.

[2] Waite, J. H., Jr., et al.: An auroral flare at Jupiter, Nature, Vol. 410, pp. 787–789, 2001.

[3] Elsner, R. F., et al.: Simultaneous Chandra X-Ray, Hubble Space Telescope Ultraviolet, and Ulysses radio observations of Jupiter's aurora, J. Geophys. Res., Vol. 110, p. A01207, 2005.

[4] Badman, S. V., et al.: Auroral processes at the giant planets: Energy deposition, emission mechanisms, Figure 2: As in Fig. 1, but for 14:30-14:40. The polar morphology and spectra, Space Sci. Rev., Vol. 187, pp. 99- emissions are distinctly fainter at this time than 179, 2015. during the 40-minute earlier period of Fig. 1. [5] Gladstone, G. R., et al.: The Ultraviolet Spectrograph on NASA’s Juno mission, Space Sci. Rev., 2014.